init with some kind of working prototype

unwind/types.py

@@ -0,0 +1,31 @@
+import re
+from typing import Union, cast
+
+import ulid
+from ulid.hints import Buffer
+
+
+class ULID(ulid.ULID):
+    """Extended ULID type.
+
+    Same as ulid.ULID, but allows initializing without a buffer, to make
+    it easier to use the class as a standard factory.
+
+    For more information about ULIDs, see https://github.com/ulid/spec.
+    """
+
+    _pattern = re.compile(r"^[0-9A-HJKMNP-TV-Z]{26}$")
+
+    def __init__(self, buffer: Union[Buffer, ulid.ULID, str, None] = None):
+        if isinstance(buffer, str):
+            if not self._pattern.search(buffer):
+                raise ValueError("Invalid ULID.")
+            buffer = ulid.from_str(buffer)
+            assert isinstance(buffer, ulid.ULID)
+
+        if isinstance(buffer, ulid.ULID):
+            buffer = cast(memoryview, buffer.memory)
+        elif buffer is None:
+            buffer = cast(memoryview, ulid.new().memory)
+
+        super().__init__(buffer)